Dielectric composition and method of making same



Patented May 10, 1949 DIELECTRIC COMPOSITION AND METHOD OF MAKING SAME Eugene Wainer, Niagara Falls, and Allen N. Salo- I mon, Malone, N. Y., assignors, by mesne assignments, to National Lead Company, New

{ York, N. Y., a corporation of New Jersey No Drawing. Application September 11, 1945, Serial No. 615,701

16 Claims.

This invention relates to ceramic dielectric materials and to methods of making the same. More particularly, it rela es to dielectric materials in which the alkaline earth titanates are the predominating constituent, said alkaline earth titanates being fluxed with small amounts of manganese dioxides.

In previous applications, Serial No. 465,387, now Patent No. 2,467,169, filed November 12, 1942, and Serial No. 482,613, filed April 10, 1943, now Patent No. 2,420,692, granted May 20, 1947, the useful properties of the alkaline earth titanates and mixtures of these titanates for electrical use were detailed. They are used as radio capacitors, temperature compensators, wave guides and the like, in electromechanical devices, etc. They are particularly useful because of the extremely high dielectric constants they develop coupled with low power factors and good leakage resistances.

'Most of these products are relatively pure compounds and are formed ceramically. Their firing temperatures are relatively high and difficulty is experienced in finding a flux which is not only an aid ceramically but which will not reduce the quality of the electrical properties of the final product. We have found that the addition of a very small quantity of manganese dioxide to these titanates and mixtures thereof, not only serves as an excellent flux ceramically but is unique in that its use actually improves the electrical characteristics generally of the final product, increasing the available dielectric constant and lowering the power factor along with some reduction in firing temperature. To this end, therefore, the effect of manganese dioxide may be considered unique.

In the practice of our invention We use the ceramically prepared alkalineearth titanates as the basic materials. Generally these are the titanates of calcium, strontium, and barium and ixtures thereof, particularly certain bariums rontium titanates. As the source of manganese we prefer to use chemically prepared manganese dioxide though very pure pyrolusite mineral of about 96% M1102 content is also suitable.

The finely ground ingredients, as indicated in the table below, are thoroughly mixed in and the damp powder is granulated by passage through a 20 mesh screen. The granulated mixture is pressed into standard one-inch disc capacitors about one-tenth inch thick at 4000 pounds per square inch and dried, and then fired to the temperatures indicated in the table, holding at maturation temperature for 3 hours. After cooling, silver electrodes are applied at opposite sides of the disc and the electrical characteristics measured at the designated radio frequencies.

'In thefollowing table are presented the data obtained by addition of about 0.05% to 1% M1102 to special compositions of the titanates of the alkaline earth metals at temperatures from 2350 F. to 2550 F. Such addition permits the formation of non-porous dielectric materials at temperatures below that at which ceramic union occurs without the presence of manganese dioxide. Although complete data is given herein for the electrical characteristics of certain special mixes of titanates, addition of manganese dioxide to all ranges of mixtures of titanates, or to individual titanates alone, lowers the firing temperature required to produce the ceramic and improves the electrical properties.

TABLE Example I I'Mega'c'yclc Parts 'Firing' Parts of T1tanate M1102 Temp. Dielec Tower trio Constant Factor 1 Percent porous porous porous porous 3,090 0.51 2, 590 0.34 3, 530 0.24 3,4 0 0.13 2, 640 0.32 3,570 0. 22 ,690' 10.29 2, 820 0. a2 3, 380 0.-;34 3,390 0.22 2, 820 0.29 3,010 0.42 3,050 0.57 2,605 0.29 2,570 0.32 2,430 0.34

Example- II lMegacycle Parts Firin Parts of T1tanate M1102 Temp .Dielem Power me Factor Constant F. Percent 19 69 BaTiO 31 SrliO3 2,350 .porous "porous 20 do 2,450 porous porous 4,420 0.168 porous porous porous porous 5, 0. 51 porous porous porous porous 6, 480. 0.148 730 0:39 4, 590 0.47 5,480 0. 35 3,560 0:37 4,480 0;;44 4, 00 0. 53 3,140 0. 27

Example III Example VI 1 Megacycle 1 Megaoycle Firing Parts of Trtauate Temp i z Power Parts of Trtanate Dielem ower 1'10 T10 Constant Factor Constant Factor F. Percent Percent 71 BtlTiOa, 29 SrTiO m 2, 350 porous porous BaTiOa, good grade porous porous do 2, 450 porous porous do 0.93 2, 550 4, 460 0. 49 1, 600 0. 89 0. 05 2, 350 2, 760 0. 77 0. 05 porous porous 0. 05 2, 450 4, 360 0. 77 0.05 1, 560 1. 18 0.05 2, 550 4, 540 0. 76 0. 05 1, 710 1, 31 0. 350 2, 790 0. 65 0. 10 porous porous 0. 10 2, 450 4, 440 0. 76 O. 1 1, 680 1, 37 0. 1O 2, 550 4, 560 0. 75 0. 1 1, 740 1. 38 0. 3D 2, 350 2, 750 0. 41 0. 3 porous porous 0. 2, 450 5, 030 0. 48 0.3 1, 450 0.90 0. 30 2, 550 4, 890 0. 47 0. 3 1, 700 1. 20 0. 50 2, 350 2, 670 0. 44 0. 5 porous porous 0. 50 2, 450 5, 070 0.49 0. 5 1, 520 0.92 0. 50 2, 550 4, 520 0. 5O 0. 5 1, 720 1. 05 1. 00 2, 350 2, 330 0.45 1. 0 porous porous 1. 00 2, 450 4, 030 0.45 1.0 1, 505 0. 62 1. 00 2, 550 2, 000 0.97 1. 0 1, 710 1. 35

Example IV Example VII 1 Megaoycle 1 Megacycle Firing Parts of Trtanate Temp Disk? Power Parts of Trtanate Die1ec Power trrc Factor tric Factor Constant Constant F. Percent Percent 73 BaTiOa, 27 Sr'IiO 2,350 porous porous BaTio poor grade..- 957 57 do 2,450 2, 160 0.70 ..-..do 1,100 0. 57 2, 550 3, 060 0. 58 1, 140 O. 64 0. 05 2, 350 2, 000 0. 97 0. 05 1, 030 0. 60 0. 05 2, 450 3, 490 0.75 0.05 1, 130 0.67 0.05 2, 550 3, 460 0. 0.05 1, 240 0. 81 0. 1 2, 350 2, 200 0. 91 0. 1 1, 050 0. 63 0.1 2, 450 610 0. 82 0.1 1, 155 0.65 0. 1 2, 550 3, 650 0. 69 0. 1 1, 230 0. 84 0.3 2, 350 2, 150 0.71 0. 3 1, 137 0.89 0.3 2, 450 3, 970 0. 62 0. 3 1, 312 0.91 0.3 2, 550 3, 810 0.52 0.3 1, 375 1. 19 0.5 2, 350 2, 090 0.57 0. 5 1,130 1. 02 0. 5 2, 450 3, 960 0.71 0. 5 1, 270 1. 00 0.5 2, 550 4, 030 0. 77 0. 5 1, 320 1. 24 1. 0 2, 350 2, 180 0. 70 1. 0 1, 110 0. 98 1. O 2, 450 3, 710 0. 94 1. O 1, 200 0. 97 1.0 2, 550 4, 160 0. 1. 0 1, 220 1. 02

Example V Example VIII 1 Megaoycle 1 Megacycle Firing Parts of Tltanate Temp Dzelw Power Parts of Trtanate i Power no no Constant Factor Constant Factor F. Percent Percent 73 2, 350 porous porous porous porous 74 2, 450 porous porous 159 0. 021 75 2, 550 2, 250 0. 72 156 0. 027 76 05 2, 350 porous porous 0. 05 porous porous 77 0. 05 2, 450 15 1. 15 0. 05 165 0.018 78 0. O5 2, 550 2, 010 0. 93 0. 05 167 0. 018 79 O. 1 2, 350 porous porous 0. 1 porous porous 8O 0. 1 2, 450 2, 260 1. 14 0. 1 154 81 0. 1 2, 550 2, 0. 92 O. 1 159 0. 015 82 0.3 2, 350 2, 640 0. 64 0. 3 porous porous 83 0. 3 2, 450 2, 600 0. 85 0. 3 156 0. 027 84 0.3 2, 550 2. 410 0. 72 0. 3 161 0.019 85 0. 5 2, 350 2, 810 0. 57 0. 5 porous porous 86 0. 5 2, 450 2, 630 0. 75 0. 5 0. 031 87 0. 5 2, 550 2, 640 0. 74 0. 5 169 0. 028 88 1. O 2, 350 2, 850 O. 49 1. 0 porous porous 89 1. O 2, 450 3, 380 0. 54 1. 0 1 0. 053 90 1. 0 2, 550 2, 960 0. 51 1. 0 0. 057

Example IX 1 Megacycle Parts Firing Parts of Titanate M7102 T mp Dielec- Power tnc Factor Constant F. Percent 2, 350 porous porous 2, 450 230 O. 08 2, 550 244 0. 04 O. 05 2, 350 porous porous 0. 05 2, 450 272 0.03 O. 05 2, 550 264 0. 02 0. 1'0 2, 350 porous porous 0.1 2, 450 254 0. 04 0. l 2, 550 252 0.03 0. 3 2, 350 porous porous J3 2, 450 273 0. O3 0. 3 2, 550 252 0. O4 0. 5 2, 350 porous porous 0. 5 2, 450 269 0.08 0. 5 2, 550 261 0.04 l. 0 2, 350 244 O. 04 l. 0 2, 450 272 0. 04 l. 0 2, 550 258 0.03

addition of MnOz to the raw batch is given.

Example X Grams Grams BaCOs 197 BaCOs 197 'IiOz 80 T102 80 MnO2 0.233

The above mixes were prepared separately, thoroughly blended, calcined 3 hours at 2250 F., wet milled through 325 mesh, dried, and standard ceramic test bodies prepared therefrom and tested as before.

The following electrical results were obtained after firing at 2450 F.

Dielectric Power Constant Factor P t A 1.004 5747 5 B 1, 242 0. 54

Example XI A B Grams Grams W SICOs 146 SrCOs 146 TiOz 80 T10 80 MnOz 0.183

These were prepared in the same fashion as the BaTiOz in Example X.

The electrical results obtained were as follows (after firing at 2450 F.) 1

Example-XII" A BY Grams Grams. C'aCO's 99 CaCO's 99. TiOz T102 80 MnOz 0.136

These were prepared'in the same fashion as'the BaTiOa in Example X.

The electrical results obtained after firing the test pieces at 2450 F. were as follows:

These were prepared as indicated in the preceding examples. The ceramic test capacitors prepared therefrom were fi'redat 2550 F. The electrical results. obtained atl megacycle were as follows:

Dielectric Power Constant Factor Percent It will be understood that the foregoing examples are merely illustrative of the principles of the invention and are not deemed limitative thereof. An infinite number of mixes of the titanates is available and addition of a small quantity of manganese dioxide to either the individual titanate or mixtures of titanates will be found to be beneficial.

What is claimed is: I

1. The ceramic dielectric consisting of an alkaline earth metal titanate and from 0.05% to 1% by weight of manganese dioxide.

2. A ceramic dielectric consisting of barium titanate and from 0.05% to 1% by weight of manganese dioxide.

3. A ceramic dielectric consisting of strontium titanate and from 0.05% to 1% by weight of manganese dioxide.

4. A ceramic dielectric consisting of calcium titanate and from 0.05% to 1% by weight of manganese dioxide.

5. A ceramic dielectric consisting of a mixture of alkaline earth titanates and from 0.05% to 1% by weight of manganese dioxide.

6. A ceramic dielectric consisting of a mixture of barium titanate, another alkaline earth metal titanate and from 0.05 to 1 by Weight of manganese dioxide.

7. A ceramic dielectric consisting of a mixture of strontium titanate, another alkaline earth metal titanate and from 0.05% to 1% by weight of manganese dioxide.

8. A ceramic dielectric consisting of a mixture of calcium titanate, another alkaline earth metal titanate and from 0.05% to 1 by weight of manganese dioxide.

9. A method of manufacturing a ceramic die electric which comprises firing a mixture consisting of an alkaline earth metal titanate with from 0.05% to 1% by weight of manganese dioxide at a temperature within the range 2350 F. to 2550 F.

10. A method of manufacturing a ceramic dielectric which comprises firing a mixture consisting of barium titanate with from 0.05% to 1% by weight of manganese dioxide at a temperature within the range 2350 F. to 2550 F.

11. A method of manufacturing a ceramic dielectric which comprises firing a mixture consisting of strontium titanate with from 0.05% to 1% by weight of manganese dioxide at a temperature within the range 2350 F. to 2550 F.

12. A method of manufacturing a ceramic dielectric which comprises firing a mixture consisting of calcium titanate with from 0.05% to 1% by weight of manganese dioxide at a temperature within the range 2350 F. to 2550 F.

13. A method of manufacturing a ceramic dielectric which comprises firlng a mixture consisting of alkaline earth metal titanates with from 0.05% to 1% by weight of manganese dioxide at a temperature within the range 2350 F. to 2550 F.

14. A method of manufacturing a ceramic dielectric which comprises firing a mixture consisting of barium titanate and another alkaline earth metal titanate with from 0.05% to 1% by weight of manganese dioxide at a temperature within the range 2350 F. to 2550 F.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,215,478 Rath et a1. Sept. 24, 1940 2,220,765 Hirose et a1. Nov. 5, 1940 FOREIGN PATENTS Number Country Date 396,532 Great Britain 1933 588,271 Germany 1933 445,495 Great Britain 1936 Certificate of Correction Patent No. 2,469,584. May 10, 1949.

EUGENE WAINER ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 49, claim 1, for the words The ceramic read A ceramic; o. o 7

wand that the said Letters Patent should be read with this correction therein that the same may conform to the record of the casein the Patent Oflice.

Signed and sealed this 1st day of November, A. D. 1949.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents. 

